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HIGH POWER SINGLE MODE SEMICONDUCTOR LASERS FABRICATED BY MO-CVD

Publishing Venue

Xerox Disclosure Journal

Abstract

Based upon tests of mesa waveguide semiconductor lasers of the type disclosed in US. Patent 4,433,417 and grown by MO-CVD, lateral spatial thickness variations (LSTV) in the active region of the laser can be induced by the growth conditions and surface kinetics at the growth interface. Such LSTVs can result in excellent waveguide structures due to the slight differences established in the lateral index of refraction causing laser operation to occur in the thickest portion of the laser active region. This not only provides good waveguiding but also results in an increase in charge diffusion into the lasing region, resulting in the lowering of lasing threshold.

Country

Undisclosed

Language

English (United States)

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HIGH POWER SINGLE MODE SEMICONDUCTOR LASERS FABRICATED BY MO-CVD (Cont'd)

Based upon tests of mesa waveguide semiconductor lasers of the type disclosed in US. Patent 4,433,417 and grown by MO-CVD, lateral spatial thickness variations (LSTV) in the active region of the laser can be induced by the growth conditions and surface kinetics at the growth interface. Such LSTVs can result in excellent waveguide structures due to the slight differences established in the lateral index of refraction causing laser operation to occur in the thickest portion of the laser active region. This not only provides good waveguiding but also results in an increase in charge diffusion into the lasing region, resulting in the lowering of lasing threshold.

The drawback, however, is that these lasers experience a catastrophic damage limit at about 23 mW to 30 mW, owing to their tightly confined optical beam having, for example, half power beam widths of approximately 2,um. This limits the usefulness of these lasers for very high power applications.

We describe here a solution to this problem utilizing laser configurations which, owing to LSTV and to unique positioning of the current confining stripe over the thinnest portion of the active region, a stable lowest order mode with a half power width greater than 4pm may be obtained, leading to at least a doubling of the output power level.

Examples of configurations employing the appropriate geometry are shown in Figures 1 and 2. Referring to Figure 1, the semiconductor laser 10 comprises a substrate 12 and MO-CVD epitaxially deposited cladding layer 14, active layer 16, cladding layer 18 and cap layer 20. A proton implant region 22 is formed through cap layer 20 and into cladding layer 18. Laser contacts are not shown. An LSTV active region 21 is created in active layer 16 by providing, prior to growth, a mesa 13 of width W and height H on the surface of substrate 12. A current conducting channel 24 of width S is positioned over the thinnest portion 21A of active region 21. To be noted from this MO-CVD growth are the thicker "ears" at the edge portions 23 of active region 21. The ihinnest portion 21A central of the active region 21 may be approximately lOOOA-thick while the thickest portions at the "ears" 23 may be approximately 110OA. The width S of channel 24 may be approximately 4 um. Th...